The present invention relates to vehicle steering linkages usable in conjunction with a twin I-beam vehicle suspension system and, more particularly, to a lateral steering linkage usable in conjunction with the twin I-beam vehicle suspension.
For purposes of vehicle handling, it is desirable that vehicle wheel toe changes due to driving conditions be controlled. Ideally, wheel toe changes produced during in-phase wheel motion or ride motion (i.e., during simultaneous up and down motion of both front wheels) should produce no net steer effect in either the right or left directions. Also, it is desirable that wheel toe changes produced during both out-of-phase wheel motion or roll motion (i.e., up and down motion of each separate wheel) produce a net steer effect tending to move the wheels out of the turn direction (a net understeer effect).
Vehicles incorporating a twin I-beam (TIB) suspension system typically employ a steering system which includes an asymmetric steering linkage (for example, a Haltenberger steering linkage, as seen in FIG. 1). One limitation of the Haltenberger steering linkage as used with the TIB suspension is its inability to provide satisfactory wheel toe response curves during both in-phase wheel motion and out-of-phase wheel motion. In a steering system using a Haltenberger linkage, to prevent undesirable wheel toe changes during ride motion, it is necessary to configure the steering geometry so as to minimize or prevent any wheel toe change. However, when the steering geometry is designed to produce zero or minimum toe change during ride motion, the toe changes due to wheel roll motion are adversely affected such that a kinematic roll oversteer effect is produced. This results in a reduction of the contribution made by the steering system to overall vehicle understeer characteristics, thereby degrading the handling characteristics of the vehicle.